2010 Thomson medal and prize

Professor Gaetana Laricchia

University College London

For her contributions to the development of the world's only positronium beam and its use to probe the properties of atoms and molecules.

Professor Laricchia’s group are recognised as international leaders in positron physics. She pioneered the development of positronium beams and leads the only group in the world with an operational positronium beam.

She has extensively exploited the unique properties of positronium (uncharged and twice the mass of an electron) to probe the properties of atoms and molecules, performing the first measurements of both total positronium collision cross sections (using argon) and positronium break-up (using helium).

Her work on positron collision physics included measurements of near – threshold ionisation which have led to the development of new threshold laws. Her unique kinematically complete measurements (in which the energy distribution among all particles is accounted for) of direct ionisation by positron impact revealed the occurrence of electron – capture – to – the – continuum. This work also exposed an unexpected symmetry in the energy sharing between the ejected electron and the positron which theorists are still struggling to explain.